Hydrogen is expected as a future energy medium and active research and development have been done in a wide range of technical fields, such as production, storage and transportation, and use. The advantages using hydrogen as an energy medium include high energy utilization efficiency and the fact that a waste after combustion is only water.
Under the present circumstances, about 80% of primary energy is occupied by fossil fuels, such as petroleum, coal, and natural gas, and even though it will gradually decrease by the increase of use of renewable energy and the like from now on, it is expected that the high ratio will be maintained. Therefore, in the production of hydrogen, it can be said that, as a source of primary energy, the importance of the route using a fossil fuel as a raw material will not decrease for the time being.
A method of obtaining high purity hydrogen by performing a reforming reaction while extracting hydrogen using a hydrogen-permeable membrane such as Pd in a reformer for reforming fossil fuels is known as a method in which high purity hydrogen is obtained with simple apparatus (Patent Documents 1 and 2).
Such technology is effective in efficiently obtaining high purity hydrogen, but carbon dioxide is by-produced. Reduction of CO2 emission is said to be an urgent and important issue for preventing global warming. In such a situation, a technology for separating and recovering CO2 which is by-produced when hydrogen is produced from a fossil fuel is important as a technology capable of coping with both the reduction of CO2 emission and the early realization of the hydrogen society.
Patent Document 3 discloses a method in which a hydrogen-permeable membrane is used in a reformer for fossil fuels and produced carbon dioxide is separated. However, since carbon dioxide is separated by allowing it to be absorbed by an absorbent made of an alkaline compound, a complicated step with low energy efficiency was required, such as a step in which steam is used to provide heat for recovering carbon dioxide from the absorbent.    Patent Document 1: Japanese Patent Laid-Open No. H06-263402    Patent Document 2: Japanese Patent Laid-Open No. H06-345408    Patent Document 3: Japanese Patent Laid-Open No. 2002-321904